A number of devices exist which vibrate to provide a signal to a user. Examples include paging devices (e.g., pagers) and cell phones operated in a vibrate mode. Vibrating devices also exist for providing therapy to a user of the device (e.g., personal massage units, sexual aids, toothbrushes). Such devices are typically portable, and may be handheld or wearable devices. Such devices are often powered by replaceable batteries, or may alternately receive power via a power cord plugged into a standard AC wall outlet.
Power cords tend to be cumbersome, however, and may limit the range of use or portability of a device. Batteries provide enhanced portability to certain devices, although batteries wear out with use and need to be replaced periodically. Replacement of batteries requires opening a battery compartment, removing the worn batteries, and replacing them with new batteries which must be purchased separately. Battery replacement creates waste, puts additional wear and tear on the device, and may even create problems with certain devices (e.g., exposure of fluids to the battery compartment). What is needed therefore are portable vibrating devices that operate without the need for replacement batteries.